Arthroplasty systems and methods

ABSTRACT

Systems for joint arthroplasty include prostheses which are secured to bone with sliding anchors. Examples include unicondylar and bicondylar knee prostheses for hemi-arthroplasty and total arthroplasty. Instruments guide the anchors into proper engagement with the prosthetic components. Methods of using the prostheses and instruments are disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of:

U.S. patent application Ser. No. 13/328,592, filed Dec. 16, 2011,entitled ARTHROPLASTY SYSTEMS AND METHODS, which is pending.

U.S. patent application Ser. No. 13/328,592 claims the benefit of:

U.S. Provisional Patent Application No. 61/423,827, filed Dec. 16, 2010,entitled TIBIAL TRAY FIXATION;

U.S. Provisional Patent Application No. 61/442,464, filed Feb. 14, 2011,entitled SYSTEM AND METHOD FOR TIBIAL TRAY FIXATION; and

U.S. Provisional Patent Application No. 61/450,753, filed Mar. 9, 2011,entitled FEMORAL AND HEMI-ARTHROPLASTY FIXATION USING ANCHOR TECHNOLOGY.

The above referenced documents are hereby incorporated by reference intheir entirety.

BACKGROUND OF THE INVENTION

This disclosure relates to systems and methods for joint resurfacing,replacement, and the like. While the examples in the present disclosurerelate to the knee joint, the systems and methods are applicable toother synovial joints in the body.

Arthroplasty procedures seek to replace a natural joint that hasdeteriorated in its functionality, range of motion, weight bearing, andmost, if not all, other performance and a lifestyle attributes. Jointresurfacing typically involves removal of at least a portion of anatural articular surface of a bone in order to replace the removedtissue with a prosthesis having an articular surface that replicates atleast the removed portion of the natural articular surface. Jointreplacement may involve more extensive bone removal and subsequentreplacement with a more substantial prosthesis. In this disclosure,remarks about resurfacing are to be considered equally relevant toreplacement, and vice versa.

Arthroplasty procedures may involve one or more articular surfaces of ajoint. In the knee, for example, the medial femoral condyle, the lateralfemoral condyle, the medial tibial condyle, the lateral tibial condyle,the trochlear groove, and/or the patella may be resurfaced or replaced.A procedure may be described as unicondylar if one condyle of the jointis treated, such as the medial tibial condyle. Bicondylar procedures maytreat two condyles of a bone, such as the medial and lateral tibialcondyles. A procedure may be described as unicompartmental if onecompartment of the joint is treated, such as the medial compartment ofthe knee. Bicompartmental procedures may treat two compartments, such asthe medial and lateral compartments of the knee. A procedure may bedescribed as a total joint procedure if most or all opposing articularsurfaces of the joint are resurfaced or replaced. A procedure may bedescribed as a hemiarthroplasty procedure if the prosthetic componentarticulates against an opposing natural articular surface, such as theprosthetic medial tibial component articulating against the naturalmedial femoral condyle.

BRIEF DESCRIPTION OF THE DRAWINGS

Various examples of the present technology will now be discussed withreference to the appended drawings. It is appreciated that thesedrawings depict only typical examples of the invention and are thereforenot to be considered limiting of its scope.

FIG. 1 is a bottom perspective view of a knee tibial prosthesis with abicondylar tibial component and fixation elements;

FIG. 2A is a top view of one of the fixation elements of FIG. 1; andFIG. 2B is a side view of the fixation element of FIG. 2A;

FIG. 3A is a bottom view of the tibial component of FIG. 1; and FIG. 3Bis a top view of the tibial component of FIG. 1;

FIG. 4 is a bottom detail view of a portion of the knee tibialprosthesis of FIG. 1;

FIG. 5A is a bottom perspective view of another knee tibial prosthesiswith a bicondylar tibial component and fixation elements; and FIG. 5B isa front oblique view of the knee tibial prosthesis of FIG. 5A;

FIG. 6A is a top view of one of the fixation elements of FIG. 5A; andFIG. 6B is a side view of the fixation element of FIG. 6A;

FIG. 7 is a bottom view of the tibial component of FIG. 5A;

FIG. 8A is a bottom detail view of a portion of the knee tibialprosthesis of FIG. 5A; and FIG. 8B is a bottom perspective detail viewof the portion of the knee tibial prosthesis of FIG. 5A;

FIG. 9A is a top perspective view of the tibial component of FIG. 1engaged with a fixation element guide instrument, a portion of theinstrument not shown; and FIG. 9B is a bottom perspective view of thetibial component and instrument of FIG. 9A engaged with the fixationelements of FIG. 1, a portion of the instrument not shown;

FIG. 10 is a bottom perspective view of yet another knee tibialprosthesis with a unicondylar tibial component and a fixation element;

FIG. 11A is a side perspective view of the fixation element of FIG. 10;and FIG. 11B is a top view of the fixation element of FIG. 10;

FIG. 12A is a bottom perspective view of the tibial component of FIG.10; and FIG. 12B is a top perspective view of the tibial component ofFIG. 10;

FIG. 13A is a top perspective view of the tibial component of FIG. 10engaged with a fixation element guide instrument; and FIG. 13B is abottom perspective view of the tibial component and instrument of FIG.13A engaged with the fixation element of FIG. 10;

FIG. 14 is a side view of a knee femoral prosthesis with a bicondylarfemoral component and fixation elements;

FIG. 15 is a top view of another knee femoral prosthesis with abicondylar femoral component and fixation elements;

FIG. 16A is a side view of yet another knee femoral prosthesis with aunicondylar femoral component and a fixation element; and FIG. 16B is afront cross section view of the knee femoral prosthesis of FIG. 16Asectioned along line 16B-16B of FIG. 16A; and

FIG. 17A is a front view of another knee tibial prosthesis with aunicondylar hemiarthroplasty tibial component and a fixation element;and FIG. 17B is a bottom view of the knee tibial prosthesis of FIG. 17A.

DETAILED DESCRIPTION

In this specification, standard medical directional terms are employedwith their ordinary and customary meanings. Superior means toward thehead. Inferior means away from the head. Anterior means toward thefront. Posterior means toward the back. Medial means toward the midline,or plane of bilateral symmetry, of the body. Lateral means away from themidline of the body. Proximal means toward the trunk of the body. Distalmeans away from the trunk.

In this specification, a standard system of three mutually perpendicularreference planes is employed. A sagittal plane divides a body intobilaterally symmetric right and left portions. A coronal plane divides abody into anterior and posterior portions. A transverse plane divides abody into superior and inferior portions.

In this specification, standard knee anatomical terms are employed withtheir ordinary and customary meanings.

An example of a joint arthroplasty system includes a prostheticarticular surface which replaces at least a portion of a naturalarticular surface of a bone and a prosthetic component including abone-contacting surface. The bone-contacting surface includes at leastone undercut channel extending across at least a portion of thebone-contacting surface and through a perimeter edge of thebone-contacting surface. The system also includes an anchor with a rail,a blade, and a support. The rail has at least one lateral protrusion.The blade is offset from the rail. The support connects the rail and theblade. The rail is insertable into the channel to connect the anchor tothe prosthetic component. When the rail is inserted into the channel,the lateral protrusion plastically deforms, the support protrudesthrough the bone-contacting surface, and the blade is carried at adistance from the bone-contacting surface.

In other examples of this system, the prosthetic component may beselected from the group consisting of a knee tibial component, a kneefemoral component, and a knee patellar component. The prostheticarticular surface may be opposite the bone-contacting surface. Atransverse cross section of the channel and a transverse cross sectionof the rail may be complementary negative and positive shapes,respectively. The blade may be inclined at an acute angle relative tothe bone-contacting surface when the rail is in the channel. A leadingend of the anchor may include oblique sharpened edges. The channel mayinclude at least one shoulder formed in an edge of the channel, whereinthe shoulder deforms the lateral protrusion when the rail is insertedinto the channel.

Another example of a knee arthroplasty system includes a prostheticarticular surface which replaces at least a portion of a naturalarticular surface of a knee joint and a bone-contacting surface. Thebone-contacting surface includes at least one undercut channel extendingacross at least a portion of the bone-contacting surface and through aperimeter edge of the bone-contacting surface. The system also includesan anchor with a rail, a blade, and a support. The blade is offset fromthe rail. The support connects the rail and the blade. The rail isinsertable into the channel to connect the anchor to the prostheticcomponent. When the rail is inserted into the channel, the supportprotrudes through the bone-contacting surface, and the blade is carriedat a distance from the bone-contacting surface.

In other examples of this system, the articular and bone-contactingsurfaces may be carried by a prosthesis selected from the groupconsisting of a knee tibial prosthesis, a knee femoral prosthesis, and aknee patellar prosthesis. The prosthesis may be selected from the groupconsisting of a unicondylar prosthesis and a bicondylar prosthesis. Atransverse cross section of the channel and a transverse cross sectionof the rail may be complementary negative and positive dovetail shapes,respectively. The blade may be inclined at an acute angle relative tothe bone-contacting surface when the rail is in the channel. A leadingend of the anchor may include oblique sharpened edges. When the rail isinserted into the channel, the rail may seize in the channel.

An example of a method of preparing a joint arthroplasty prosthesis forreplacing at least a portion of a natural articular surface of asynovial joint includes providing a prosthesis with a bone-contactingsurface and an articular surface, the bone-contacting surface includingat least one undercut channel extending across at least a portion of thebone-contacting surface and through a perimeter edge of thebone-contacting surface, the articular surface replicating at least aportion of a natural articular surface of a synovial joint; providing ananchor including a rail, a blade, and a support, the rail including atleast one laterally protruding tab, the blade offset from the rail, thesupport connecting the rail and the blade; sliding the rail into thechannel, wherein the tab plastically deforms as the rail slides into thechannel; and sliding a portion of the support into the channel, thesupport protruding through the bone-contacting surface, wherein aportion of the bone-contacting surface is spaced between the blade andthe rail when the rail and the support are in the channel.

In other examples of this method, sliding the rail into the channel maybe performed before sliding the portion of the support into the channel.Sliding the rail into the channel may include sliding the tab past ashoulder formed in an edge of the channel. The shoulder may deform thetab. The blade may be inclined at an acute angle relative to thebone-contacting surface when the rail is in the channel. The acute anglemay open toward a leading end of the anchor. The method may also includeproviding a guide tool including an attachment portion and a guidanceportion. The attachment portion may be releasably attachable to aportion of the prosthesis. The guidance portion may include at least onetrack. The method may also include attaching the attachment portion tothe prosthesis. The track may coaxially align with the channel when theattachment portion is attached to the prosthesis. The method may alsoinclude inserting the rail into the track and sliding the anchor towardthe prosthesis. Attaching the attachment portion to the prosthesis mayinclude attaching a clip to the attachment portion and snapping the clipto the prosthesis.

Another example of a method of replacing at least a portion of a naturalarticular surface of a synovial joint includes forming a resectionsurface on a bone of the synovial joint to remove at least a portion ofthe natural articular surface of the bone; positioning a bone-contactingsurface of a prosthesis against the resection surface; positioning anarticular surface of the prosthesis to replace the removed naturalarticular surface; and installing an anchor to fix the prosthesis to thebone. Installing the anchor includes sliding a rail of the anchor intoan undercut channel of the prosthesis, the channel extending through aperimeter edge of the bone-contacting surface and across at least aportion of the bone-contacting surface, wherein a laterally protrudingtab of the rail plastically deforms as the rail slides into the channel;sliding a blade of the anchor into the bone, wherein portions of thebone-contacting surface and the resection surface become situatedbetween the blade and the rail portion as the blade slides into thebone; and sliding a support of the anchor into the channel and the bone,the support connecting the blade to the rail.

In other examples of this method, sliding the rail into the channel maybe performed before sliding the blade into the bone, which may beperformed before sliding the support into the channel and the bone.Sliding the rail into the channel may include sliding the tab past ashoulder formed in an edge of the channel, wherein the shoulder deformsthe tab. The blade may be inclined at an acute angle relative to thebone-contacting surface when the rail is in the channel, wherein theacute angle opens toward a leading end of the anchor. The method mayalso include providing a guide tool including an attachment portion anda guidance portion, the attachment portion releasably attachable to aportion of the prosthesis, the guidance portion including at least onetrack; attaching the attachment portion to the prosthesis, wherein thetrack coaxially aligns with the channel when the attachment portion isattached to the prosthesis; inserting the rail into the track; andsliding the anchor toward the prosthesis. Attaching the attachmentportion to the prosthesis may include attaching a clip to the attachmentportion and snapping the clip to the prosthesis.

This disclosure relates to systems and methods for joint resurfacing,replacement, and the like. This disclosure sets forth examples of jointprostheses with adjunctive fixation elements, or anchors. The anchorsmay contribute to initial and/or long term fixation of a prostheticcomponent to bone. The fixation elements may provide fixation alone, orin combination with other fixation means, such as bone cement orbiological fixation to porous coating, to name just two examples. Eachfixation element may be inserted into a complementary slot in theprosthetic component so that the fixation element protrudes from theprosthetic component into the adjacent bone. The fixation elements maybe used in lieu of bone screws for component fixation.

Referring to FIG. 1, a knee tibial prosthesis 10 includes a tibialcomponent 50 and at least one fixation element 20. The tibial component50 may be referred to as a tibial tray 50. The tibial prosthesis 10 ofFIG. 1 includes two fixation elements 20, which may also be referred toas anchors 20. The anchors 20 may be inserted from an anterior edge 54of the tibial tray 50 and may be oriented roughly anterior-posterior, asshown. The anchors 20 may be parallel or angled relative to one anotherand/or the tray 50. For example, the anchors 20 of FIG. 1 are angledrelative to one another, with the anchors closest together at theanterior edge 54 of the tibial tray 50. The anchors may also be tiltedwith respect to the tray 50, for example, tilted laterally. The anchors20 are inserted in channels 52 in the tibial tray 50. The channels maybe dovetailed as shown; other undercut channel geometries arecontemplated, such as T-slots. The channels 52 of FIG. 1 extend betweenanterior and posterior edges 54, 66 of the tray 50. In some embodiments,the channels may only open at one of the anterior and posterior edges54, 66, and may terminate in the main body of the tray 50. In otherexamples, the channels 52 may be oriented exactly anterior-posterior,exactly medial-lateral, roughly medial-lateral, or in anotherorientation. A channel 52 may open through any perimeter edge of abone-contacting side 56 of the tray 50.

The anchors in the present disclosure may share some or all of thefeatures of the anchors disclosed in U.S. patent application Ser. No.12/640,892 to Bae, et al., which is incorporated by reference herein inits entirety.

Referring to FIGS. 2A and 2B, each fixation element or anchor 20comprises a blade 22 and a rail 24. The blade and rail extend between aleading end 70 and a trailing end 68 of the anchor. The leading end 70may also be referred to as a distal end 70; the trailing end 68 may alsobe referred to as a proximal end 68. Supports 26 connect the blade 22 tothe rail 24. FIGS. 2A and 2B illustrate an anchor 20 with three supports26, although other examples may include any number of supports. Thesupports 26 define apertures 27 through the anchor 20. In use, the blade22 and at least a portion of the supports 26 may be inserted into bone.The blade 22 may be pointed, sharpened, and/or serrated, for ease ofinsertion into bone. The supports 26 may also be sharpened and/orobliquely profiled for ease of insertion into bone. The blade edges maybe beveled. The blade 22 may be pierced by one or more apertures 36.Longitudinal edges 28 of the rail may be sized and shaped forcomplementary engagement with the dovetail channels 52 of the tray 50.In other examples, the rail may be of a complementary size and shape toengage another undercut channel geometry.

There may be a small tab 30 projecting from the rail 24. The tab may besaid to protrude laterally or transversely from the rail 24. The tabdeforms as the anchor is driven into the tibial tray 50, creating aninterference fit. This material deformation serves to take up anyrelative motion between the anchor and the tibial tray as well as tolock the anchor 20 into the tray 50. The deformation may becharacterized as plastic deformation, which may be at least partiallyirreversible. The deformation may cause galling, spot welding, and/orseizing to occur between the tab and the channel 52. Any of theseadhesive phenomena may lock the anchor to the tray. There may be aphysical stop 32 on the anchor to prevent over-insertion. A distal tip34 of the anchor rail may be tapered for ease of insertion into, andmovement along, the channels 52. In FIGS. 2A and 2B, tabs 30 are locatedon each side of the rail near the proximal end 68 and physical stops 32are immediately proximal to each interference tab 30. Another examplemay include a tab 30 on only one side of the rail. Other examples mayinclude multiple interference tabs 30 along the length of the rail 24.This arrangement may provide even greater fixation along the length ofthe anchor in the channel 52. Also, in other embodiments the length,height, or other dimensions of the anchor may vary.

To achieve optimal compression between the bone and the tibial tray, theanchor blade 22 may be angled divergent from the rail 24. At theleading, distal end 70 of the anchor 20, the blade 22 and the rail 24may be farther apart than they are at the trailing, proximal end 68 ofthe anchor. The divergence angle 72 may be less than about 90 degrees.In some examples, the divergence angle may be less than about 15degrees, less than about 5 degrees, or less than about 2 degrees. In theembodiment shown, the divergence angle between the blade 22 and the rail24 is 1 degree. Divergence angles of less than 1 degree are alsocontemplated.

When the anchor rail 24 is inserted into the channel 52 of the tibialtray 50, the anchor blade 22 may diverge from an inferior orbone-contacting side 56 of the tray 50 at the same angle 72.Alternatively, the blade 22 may diverge from the inferior orbone-contacting side of the tray 50 at another angle, which may begreater than or less than the blade-to-rail divergence angle 72.Furthermore, the blade-to-tray divergence angle may open in the same oropposite direction as the blade-to-rail divergence angle 72.

The angle 72 between the blade 22 and the rail 24, and/or the anglebetween the blade and the bone-contacting side 56 may correlate to themechanical properties of the bone into which the anchor 20 will beinserted, the desired amount of compression between the bone and thebone-contacting side, the compliance of the bone-contacting side, and/orother factors. For example, larger divergence angles may be appropriatefor conditions such as: softer bone, greater compression, and/or acompliant bone-contacting side; smaller divergence angles may beappropriate for conditions such as harder or stiffer bone, lesscompression, and/or an unyielding bone-contacting side. The divergenceangle may also correlate to the length of the anchor 20, with greaterdivergence angles possible with shorter anchors and smaller divergenceangles suitable for longer anchors.

Referring to FIGS. 3A and 3B, the tibial tray 50 includes abone-contacting, or inferior side 56 across which the channels 52 arerecessed. At one end of each channel 52, shoulders 59 are formed in theedges of the channels 52. In FIGS. 3A and 3B, the shoulders 59 areformed in interior edges of the channel near the anterior edge 54 of thetibial tray 50. As seen in FIG. 4, when the anchor rails 24 are insertedthrough the channels, the shoulders 59 deform the tabs 30 and engagewith the stops 32 to provide the interference fit between the anchors 20and the tray 50, and to properly position the anchors at the correctdepth relative to the tray. A stem 58 provides further fixation of thetray 50 in the tibia.

The tibial tray 50 further includes a joint-facing, or superior side 60to which an articular insert (not shown) may be mounted. A raised rim 62encompasses the superior side 60, and overhangs 64 are formed on aportion of the rim 62 for engagement with an articular insert and/orinstruments. Tibial tray 50 may be described as a bicondylar tibialcomponent because it is adapted to extend across an entire resectedtibial plateau to replace the medial and lateral condyles.

In other embodiments, the features of the tibial tray 50 may vary. Forexample, the stem 58 or other fixation features may vary; the size andthickness of the tray 50 may vary, the outer peripheral size and shapemay vary. Different connection features for engagement with an articularinsert may be incorporated. Other features of tibial trays known in theart may be included as desired. The articular insert may carry theprosthetic articular surface.

FIGS. 5A and 5B depict another example of a knee tibial prosthesis 100which includes a tibial component 150, or tray 150, and at least onefixation element 120. Except for differences in channels for receivingthe anchors, tibial tray 150 may be essentially identical to tray 50 andas such will not be further described. Similarly, the anchors 120 may beidentical to anchors 20, with the exception of a spring feature 125which may substitute for the tabs 30 and stops 32 formed on anchor 20.

Referring to FIGS. 6A and 6B, anchor 120 includes blade 122 and rail124. Spring feature 125 is formed on the rail, and comprises a pair oftabs 130 separated by a gap 131. The spring feature 125 may be locatedat a proximal end 168 of the anchor 120, which may also be called atrailing end 168. A stop 132 may be formed on the rail. The stop 132 maybe on a tab 130, as shown, or elsewhere. An opening 134 may be formedthrough the tabs 130 to provide a connection feature for anchorinsertion and/or removal instruments.

Referring to FIG. 7, tray 150 includes channels 152 for receivinganchors 120. Curbs 158 may be present on either side of the channel 152,the curbs effectively narrowing a portion of the channel. Curbs 158 areillustrated near an anterior edge 154 of the tibial tray 150, but may belocated elsewhere along the channel. Shoulders 159 may also be locatedon either side of the channel 152, and may be distal to, or posteriorto, the curbs 158. A clearance pocket 160 may be defined along a portionof the channel 152 bounded by the shoulders 159 at one end and the curbs158 at the other end.

Referring to FIGS. 8A and 8B, as anchor 120 is inserted into channel152, tabs 130 are compressed together, narrowing gap 131, as they passbetween curbs 158. Once the tabs 130 are distal to the curbs, the tabsspring apart in the clearance pocket 160. Stop 132 engages with shoulder159 to prevent further insertion of the anchor 120 distally. The stop132 near the proximal anchor end 168 may be said to index to shoulder159, which may be a flat face of the tibial tray 150, to prevent theanchor from being over-driven. Also, tabs 130 engage with curbs 158 toprevent proximal withdrawal of the anchor 120 from the tibial tray 150.The spring feature 125 prevents the anchor 120 from backing outproximally until the spring is depressed. If removal of an anchor isdesired, an instrument (not shown) may be engaged with the tabs 130 tocompress the tabs together and allow proximal withdrawal of the anchor.

To achieve optimal compression between the bone and the tibial tray, theanchor blade 122 may be angled divergent from the rail 124, in the samemanner as described for anchor 20.

Referring to FIGS. 9A and 9B, an anchor guide instrument 200 may be usedto provide guidance as the anchors slide into the channels on the tibialtray. The example shown depicts anchors 20 being inserted into tray 50;however the same instrumentation with little or no modification may beimplemented with tray 150 and anchors 120.

The anchor guide instrument 200 can attach to a polymeric (UHMW or othermedically relevant polymer) clip 220 that interfaces via a snap fit tothe superior surface 60 of the tibial tray 50. The clip 220 may engagewith the overhangs 64 on the tray to snap to the tray 50, similar to themanner in which the articular insert attaches to the tray. The anchorguide instrument 200 includes an attachment portion 222 and a guidanceportion 224. The guidance portion 224 includes two tracks 226, whichcoaxially align with the channels 52 on the tray 50 when the anchorguide instrument 200 is properly attached to the tray 50. Each anchor 20may then be inserted into a track 226 and moved distally along the trackuntil the anchor slides into channel 52. An insertion instrument may beused to tap or otherwise urge the anchor along the track and into thechannel.

In a method of use, a tibia proximal end is prepared to receive tray 50or 150. A transverse resection may be made to remove the medial andlateral proximal tibial articular cartilage. Recesses for a tray stem 58and/or fins may be reamed, drilled, broached, cut or otherwise prepared.Tray 50 or 150 is fit onto the prepared tibia, and may be implanted withor without cement. Anchors 20 or 120 are inserted into the channels onthe tray. The blades may cut into the bone as the anchors are inserted.As the anchors are inserted, the angled configuration of the anchorscauses compression of the tray toward the tibia; i.e., the tray ispulled toward the tibia. The tabs and stops on the tray and the anchorscooperate to seat the anchors at the proper depth relative to the tray,and prevent unintentional withdrawal of the anchors. An articular insert(not shown) may be coupled to the superior surface of the tray 50, andmay include an articular surface.

Referring to FIG. 2B, it can be appreciated that the act of insertinganchor 20 into channel 52 and adjacent bone may be described as asequence of events. The leading end 70 is configured so that the rail 24is the leading feature, and is thus the first feature to engage thechannel or bone. The blade 22 is the second feature to engage, as itspoint penetrates the bone. The support 26 is the third feature toengage, as it enters the channel and the bone. The support may be saidto protrude through the bone-contacting surface, since the supportextends through the open side of the channel. All leading edges of thesupport and blade are sharpened and obliquely oriented to reduce theeffort necessary to cut through the bone.

Any of the embodiments described herein may be used in a tibialprosthesis implantation procedure to provide immediate and tightfixation of the tibial component to the prepared tibia. The angledanchor blades provide immediate compression between the tibial componentand the tibia as the anchors are inserted, and may provide completefixation (no motion permitted between the tibial component and thetibia) for the time needed for bone ingrowth to occur between the tibiaand the tibial component.

Any of the tibial trays and anchors described herein may be formed oftitanium, cobalt chrome, stainless steel, or other biocompatible metalsor metal alloys, or a combination thereof. In some embodiments, theanchors may be formed of a resorbable material such as PLLA. Any of thecomponents may include a coating or treatment on part of or the entirecomponent to promote biologic/bone ingrowth.

In other embodiments, another joint replacement component may have thechannels as described above for anchoring the component to bone with theanchors disclosed herein. For example, the channels and anchorsdescribed herein may be applied to a femoral component of a kneereplacement prosthesis, a stem and/or cup component of a hip or shoulderprosthesis, ankle prostheses, elbow prostheses, or small jointprostheses. Application to all synovial joints of the body iscontemplated.

Referring to FIGS. 10-12B, another knee tibial prosthesis 320 includes aunicompartmental tibial component 310 and at least one fixation element350. In this example the fixation element may be inserted from ananterior edge of the tibial tray 310 and may run roughlyanterior-posterior. However, various anchor insertion angles arecontemplated.

The tibial component, or tray 310 may include an inferior orbone-contacting surface 312 and a joint-facing, or superior surface 314.The bone-contacting surface 312 may include at least one anti-rotationpost 315. FIG. 10 shows an example with two posts 315. Other elements,such as fins, pegs, screws, or the like may be present as well. Theposts 315, when embedded in the bone, may prevent the tibial component310 from rotating on the flat resected bone surface. The bone-contactingsurface 312 also includes at least one track 318. The track 318 isshaped to accept a complementary portion of the anchor 350. The trackand anchor portion may be any complementary guiding features, such asdovetail, T-shape, H-shape, or complementary curved features, amongothers. The track may be at least partially undercut in order to retainthe anchor in the tibial component 310.

The joint-facing surface 314 includes a negative feature, or recess 322.This feature may receive an articular insert (not shown), and may alsoengage an anchor guide instrument. There may be an undercut flange 324on a posterior side 326 of the tibial component 310, under which thearticular insert or instrument snaps to be held rigidly in the tray 310.In other embodiments, the superior surface 314 may be an integralarticular or bearing surface configured to replicate a removed naturalarticular surface, and thus configured to contact and articulate with anatural distal femur, for a hemi-arthroplasty.

Referring to FIGS. 10-11B, the anchors 350 are designed to slide intothe bone. The anchors may be pushed or impacted into the bone. Theanchor may include a longitudinal rail 356, at least one support 358,and a blade 360. The rail 356 is complementary to the track 318, and maytherefore be a dovetail, T-shape, H-shape, or complementary curvedfeature, among others. There may be at least one interference tab 354 onthe rail 356. The tab 354 deforms as the anchor 350 is driven into thetrack 318. This material deformation serves to take up any relativemotion between the anchor 350 and the tibial tray 310 as well as to lockthe anchor into the tray. In the example shown, a pair of tabs 354 isnear a trailing end 368 of the anchor 350, and another pair of tabs 354is centrally located along the rail. Other embodiments may includemultiple interference tabs 354 along the length of the rail 318. Thetrailing end 368 may also be described as the proximal end 368. Theanchor 350 also has an opposite leading end, or distal end 370. Theremay be a physical stop tab 362 on the rail. The stop tab 362 is shownimmediately proximal to the interference tab 354, although otherlocations are contemplated. As the rail 356 is inserted in the track318, the stop tab 362 may approach a matching stop feature 326 on thetray 310 which prevents insertion of the anchor 350 beyond a prescribedpoint.

To achieve optimal compression between the bone and the tibial tray 310,the anchor blade 360 may diverge from the rail 318 and/or thebone-contacting surface 312 as described for tibial prosthesis 10.

Referring to FIGS. 13A and 13B, during implantation the anchors 350 maybe guided into the appropriate tracks 318 via an anchor guide instrument380. The anchor guide 380 may attach to an anchor guide clip 390. Theclip 390 may include an engagement feature which releasably connects tothe anchor guide. The clip may also snap into the recess 322 on thetibial tray 310 and under the flanges 324, as would an articular insert.The clip 390 may be ultra-high molecular weight polyethylene (UHMWPE) orother medically relevant polymer. The anchor guide 380 includes a track382 which coaxially aligns with track 318 on the tray 310. An anchor 350may be inserted at the free end of track 382, urged distally along track382 toward the tray 310 and into track 318 on the tray. A mallet orother instrument may be used to drive the anchor into the bone materialadjacent the tibial component.

Another example of a knee tibial prosthesis may include aunicompartmental tibial tray with a plurality of tracks 318, into whicha plurality of anchors 350 may be inserted. More than one anchor may beinserted per track. Although track 318 is illustrated in FIG. 10 asextending generally anterior-posterior (A/P), it is appreciated that inother embodiments the track may extend generally medial-lateral (M/L),or along any vector between the A/P and L/M directions. Furthermore, thetrack 318 may diverge from the bone-contacting surface 312.

A knee femoral component includes at least one groove or track forengagement of an anchor which may slide into the groove and into anadjacent distal femur to anchor the femoral component to the distalfemur. The femoral component may be a unicondylar or bicondylar femoralcomponent. Anchors may be driven into grooves in the femoral componentat any location to provide fixation and/or compression of the femoralcomponent surface against the bone.

Referring to FIG. 14, a knee femoral prosthesis 400 includes an outerbearing surface 402 and an inner fixation surface 404. The bearingsurface 402 may also be called an articular surface or a joint-facingsurface. The inner fixation surface 404 may also be called abone-contacting surface. The fixation surface 404 may include multiplesegments 406. Each inner surface segment 406 may be aligned along adifferent plane, or may be coplanar with at least one other segment. Atleast one segment 406 includes a track 318 shaped to hold an anchor 350as described above. The track(s) 318 may run medial-lateral across theinner fixation surface 404 as shown in FIG. 14, although othertrajectories are envisioned, such as anterior-posterior,superior-inferior, or along an intermediate trajectory. The anchors 350may be driven into the tracks 18, providing fixation and/or compressionof the femoral component to the bone.

FIG. 15 shows a top-down view of another knee femoral prosthesis 500which includes a femoral component 510 and at least one anchor 350. Thefemoral component 510 includes an outer bearing surface 502 and an innerfixation surface 504. The bearing surface 502 may also be called anarticular surface or a joint-facing surface. The inner fixation surface504 may also be called a bone-contacting surface. Component 510 includesat least one track 318. In this example, two tracks 318 extendmedial-lateral across the fixation surface 504. Two anchors 350 areshown engaged in one of the tracks 318 toward a posterior aspect 514 ofthe femoral component 510. In other embodiments, three anchors 350 couldbe engaged in the posterior track 318. The anchors 350 may be insertedfrom either or both of the medial or lateral sides of the implant. Theprosthesis 500 also includes an elongated anchor 410 engaged in theother track 318 toward an anterior aspect 512 of the femoral component510. In other embodiments, multiple anchors 350 could be used in placeof the elongated anchor 410, and vice versa. In other embodiments, thetracks and anchors may be angled relative to the medial-lateraldimension of the femoral component, and may be inserted from any edge,whether medial, lateral, anterior, posterior, or intermediate. Thelength, width, height, and/or other dimensions of the anchor 350, 410may be appropriately scaled for the selected placement location on thecomponent and the adjacent bone portion.

Referring to FIGS. 16A and 16B, lateral and anterior views of aunicondylar knee femoral prosthesis 418 are shown. Prosthesis 418includes a unicondylar femoral component 420 and at least one fixationelement 350. Femoral component 420 includes an outer bearing surface 422and an inner fixation surface 424. The bearing surface 422 may also becalled an articular surface or a joint-facing surface. The innerfixation surface 424 may also be called a bone-contacting surface. Atleast one anchor peg 426 may protrude from the inner fixation surface424. The illustrated example shows two pegs. The anchor 350 is engagedin a tapered dovetail track 318 on the inner fixation surface 424 toprovide fixation and compression of the femoral component 420 againstthe bone. Although one fixation anchor 350 is shown, in otherembodiments multiple fixation anchors 350 may be engaged in one or moretracks 318. The anchor 350 may be inserted into the track 318 and theadjacent bone from the lateral or medial side of the femoral component420.

A tibial hemiarthroplasty component includes at least one groove ortrack for engagement of an anchor which may slide into the groove andinto an adjacent proximal tibia to anchor the component to the proximaltibia.

Referring to FIGS. 17A and 17B, a unicondylar hemiarthroplasty kneetibial prosthesis 428 is shown. The prosthesis 428 includes a tibialcomponent 430 and at least one fixation element 350. The tibialcomponent 430 includes a track 318 to receive an anchor 350. The track318, anchor 350 and insertion techniques may be the same as thosedescribed above with regard to FIGS. 10-16B. The tibial component 130has a superior side 434 and an inferior side 436. The superior side 434may be metal and it may form a bearing surface for articulation with anatural distal femur. It is appreciated that as needed, a singlehemi-arthroplasty component 430 may be implanted for a unilateralhemiarthroplasty, or two generally mirror-image components may beimplanted for a bilateral hemiarthroplasty.

In any of the examples described above, the anchors may vary in geometryand angle (for compression). The anchors may be positioned anywherealong the relative implants, i.e. medial, lateral, anterior, posterioror intermediate. Also, the dovetail track could have a differentgeometry than a taper dovetail. The extent of compression achieved maybe adjusted by varying the angle of the blade. Advantageously, use ofthe disclosed anchor may prevent osteolysis, as no pathway forosteolysis is provided, unlike in screw-based fixation systems. Thenumber of anchors used in a track or implant may vary.

The present technology may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. It isappreciated that various features of the above described examples can bemixed and matched to form a variety of other alternatives. As such, thedescribed examples are to be considered in all respects only asillustrative and not restrictive. The scope of the invention is,therefore, indicated by the appended claims rather than by the foregoingdescription. All changes which come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

The invention claimed is:
 1. A joint arthroplasty system, comprising: aprosthetic articular surface which replaces at least a portion of anatural articular surface of a bone; a prosthetic component comprising abone-contacting surface configured to compliment a resected or flattenedbone surface, the bone-contacting surface comprising at least oneundercut channel extending across at least a portion of thebone-contacting surface and through a perimeter edge of thebone-contacting surface; and an anchor comprising a rail, a blade, and asupport, the rail comprising at least one lateral protrusion, the bladeoffset from the rail, the support connecting the rail and the blade;wherein the rail is insertable into the channel to connect the anchor tothe prosthetic component; wherein, when the rail is inserted into thechannel, the support protrudes through the bone-contacting surface, andthe blade is carried at a distance from the bone-contacting surface,characterized in that the lateral protrusion is adapted such that, whenthe rail is inserted into the channel, the lateral protrusionplastically deforms to create an interference fit in the channel.
 2. Thesystem of claim 1, wherein the prosthetic component is selected from thegroup consisting of a knee tibial component, a knee femoral component,and a knee patellar component.
 3. The system of claim 1, wherein theprosthetic articular surface is opposite the bone-contacting surface. 4.The system of claim 1, wherein the channel comprises at least oneshoulder formed in an edge of the channel, wherein the shoulder deformsthe lateral protrusion when the rail is inserted into the channel. 5.The system of claim 1, wherein the system is a knee arthroplasty systemand wherein the prosthetic articular surface replaces at least a portionof a natural articular surface of a knee joint.
 6. The system of claim5, wherein the articular and bone-contacting surfaces are connected to aprosthesis selected from the group consisting of a knee tibialprosthesis, a knee femoral prosthesis, and a knee patellar prosthesis.7. The system of claim 6, wherein the prosthesis is selected from thegroup consisting of a unicondylar prosthesis and a bicondylarprosthesis.
 8. The system of claim 1, wherein a transverse cross sectionof the channel and a transverse cross section of the rail arecomplementary negative and positive dovetail shapes, respectively. 9.The system of claim 1, wherein the blade is inclined at an acute anglerelative to the bone-contacting surface when the rail is in the channel.10. The system of claim 1, wherein a leading end of the anchor includesoblique sharpened edges.
 11. The system of claim 5, wherein, when therail is inserted into the channel, the rail seizes in the channel.
 12. Amethod of assembling a joint arthroplasty prosthesis for replacing atleast a portion of a natural articular surface of a synovial joint,comprising: providing a prosthesis comprising a bone-contacting surfaceconfigured to compliment a resected or flattened bone surface and anarticular surface, the bone-contacting surface comprising at least oneundercut channel extending across at least a portion of thebone-contacting surface and through a perimeter edge of thebone-contacting surface, the articular surface replicating at least aportion of a natural articular surface of a synovial joint; providing ananchor comprising a rail, a blade, and a support, the rail comprising atleast one laterally protruding tab, the blade offset from the rail, thesupport connecting the rail and the blade; sliding the rail into thechannel, wherein the tab plastically deforms as the rail slides into thechannel to create an interference fit in the channel; and sliding aportion of the support into the channel, the support protruding throughthe bone-contacting surface, wherein a portion of the bone-contactingsurface is spaced between the blade and the rail when the rail and thesupport are in the channel.
 13. The method of claim 12, wherein slidingthe rail into the channel is performed before sliding the portion of thesupport into the channel.
 14. The method of claim 12, wherein slidingthe rail into the channel further comprises sliding the tab past ashoulder formed in an edge of the channel, wherein the shoulder deformsthe tab.
 15. The method of claim 12, wherein the blade is inclined at anacute angle relative to the bone-contacting surface when the rail is inthe channel, wherein the acute angle opens toward a leading end of theanchor.
 16. The method of claim 12, further comprising: providing aguide tool comprising an attachment portion and a guidance portion, theattachment portion releasably attachable to a portion of the prosthesis,the guidance portion including at least one track; attaching theattachment portion to the prosthesis, wherein the track coaxially alignswith the channel when the attachment portion is attached to theprosthesis; inserting the rail into the track; and sliding the anchortoward the prosthesis.
 17. The method of claim 16, wherein attaching theattachment portion to the prosthesis comprises attaching a clip to theattachment portion and snapping the clip to the prosthesis.